Printers, copiers, and other image forming apparatuses can print on a variety of media. The input trays of such devices are designed to accommodate various types of media that may vary in size, thickness, weight, moisture content, beam strength, tendency to curl, surface properties, etc.
Image forming apparatuses typically include a media handling system that feeds multiple types of media through the image forming apparatus in a reliable manner. Media handling system failures may cause damaged sheets and machine shutdowns. Such failures may be caused by any number of factors. For example, inserting too much media into the image forming apparatus may disrupt the feeding process of the media handling system. Therefore, the amount of media that is fed into the machine should be controlled.
Conventional image forming apparatuses employ stationary media stack height limiters to prevent an operator from overloading the media tray, and therefore to control the amount of media inserted into the tray. By limiting the height of the media stack, stack height limiters help prevent mis-feeds, multi-feeds, or fail-to-feeds of media into the image forming apparatus. However, while conventional stack height limiters may prevent too much media from being inserted into the media tray, these limiters do not account for height variations in the media due to environmental changes, such as temperature and humidity, which may cause the media in the tray to expand. Even though the stack height was initially limited, swelling caused by these environmental changes may alter the height of the stack, causing the height to become too great to allow smooth handling of media.
When the media stack height increases beyond a desirable limit due to environmental change, stationary stack height limiters may cause a pinch point in the media at the position where the stack height limiter contacts the media. Pinch points lead to mis-feeds and fail-to-feeds of media which bind or jam the image forming apparatus. Problems with feeding the media into the image forming apparatus cause less than optimum machine performance and increase machine downtime. As a result, the increased likelihood of paper jams under certain environmental conditions is a great disadvantage of stationary media stack height limiters.